Cooling system and method for use with a fuel cell

ABSTRACT

A cooling system is provided for use with a fuel cell. The cooling system comprises a first heat exchanger fluidly connected to an outlet passage of the fuel cell. The first heat exchanger can be configured to condense at least a portion of a fluid passing through the outlet passage of the fuel cell into liquid water. The cooling system can also comprise a second heat exchanger fluidly connected to an outlet passage of the first heat exchanger and an inlet passage of the fuel cell. The second heat exchanger can be configured to cool a fluid passing into the inlet passage of the fuel cell. In addition, the outlet passage of the fuel cell and the inlet passage of the fuel cell can be fluidly connected to a cathode of the fuel cell, and the inlet passage of the fuel cell can be configured to supply water to the cathode.

This application is a divisional of U.S. patent application Ser. No.13/795,115, filed Mar. 12, 2013, which claims the benefit of U.S.Provisional Application No. 61/609,531, filed Mar. 12, 2012, which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

This disclosure is generally directed to cooling systems for use with afuel cell.

BACKGROUND

Some types of fuel cell can include an anode, a cathode, and a porousmembrane located between the anode and the cathode. The membrane isconfigured to permit a flow of select ionic species from the cathode tothe anode. In response to this movement of ions across the membrane,electrons flow from the anode to the cathode.

A fuel cell operates by reacting hydrogen at the anode and oxygen at thecathode. Oxygen can be sourced from atmospheric air and pure hydrogen isusually supplied to the anode. The reactions occurring at the cathodeand anode may generate considerable heat. To dissipate this heat,various cooling systems have been developed. One type of cooling systemuses cathode water injection (CWI), where cooling water is supplied tothe cathode of a fuel cell and allowed to mix with one or more gasessupplied to the cathode.

In addition to maintaining the fuel cell within a limited range ofoperating temperatures, a cooling system should also operate without theneed to add or remove water from the cooling system. A “water neutral”cooling system can conserve water or save operator time spent adding orremoving water.

Some traditional cooling systems are not able to efficiently providesufficient cooling and achieve a suitable water balance under alloperating conditions because a single heat exchanger is typically usedto both condense and cool water. Combining condensing and coolingfunctions into a single device is problematic because of the differingrequirements needed to maintain adequate water balance and cooling. Forexample, to remove excess water from the cooling system, a heatexchanger's fan speed is usually reduced to create a hotter exhaust gasthat can transport more water out of the cooling system. But reducingfan speed increases water temperature, which may result in a fuel celltemperature that is too high. As such, it is often difficult to removewater and prevent fuel cell overheating using traditional coolingsystems.

The present disclosure is directed to overcoming one or more of theproblems or disadvantages of the prior art cooling systems.

SUMMARY

One aspect of the present disclosure is directed to a cooling system foruse with a fuel cell. The cooling system comprises a first heatexchanger fluidly connected to an outlet passage of the fuel cell. Thefirst heat exchanger can condense at least a portion of a fluid passingthrough the outlet passage of the fuel cell into liquid water. Thecooling system can also comprise a second heat exchanger fluidlyconnected to an outlet passage of the first heat exchanger and an inletpassage of the fuel cell. The second heat exchanger can be configured tocool a fluid passing into the inlet passage of the fuel cell. Inaddition, the outlet passage of the fuel cell and the inlet passage ofthe fuel cell can be fluidly connected to a cathode of the fuel cell,and the inlet passage of the fuel cell can be configured to supply waterto the cathode.

Another aspect of the present disclosure is directed to a power system.The power system can comprise a fuel cell having a cathode fluidlyconnected to an outlet passage and an inlet passage, wherein the inletpassage can be configured to supply at least partially recirculatedwater to the cathode. The power system can also comprise a first heatexchanger fluidly connected to the outlet passage of the fuel cell,wherein the first heat exchanger can be configured to convert at least aportion of a fluid passing through the outlet passage of the fuel cellinto water. In addition, the power system can comprise a second heatexchanger fluidly connected to an outlet passage of the first heatexchanger and the inlet passage of the fuel cell, wherein the secondheat exchanger can be configured to cool a fluid passing into the inletpassage of the fuel cell.

Another aspect of the present disclosure is directed to a method ofcooling a fuel cell. The method can comprise supplying hydrogen to ananode of the fuel cell and supplying air and water to a cathode of thefuel cell, and outputting a fluid from the fuel cell, wherein at least aportion of the fluid comprises a first fluid. The method can alsocomprise supplying the first fluid to a first heat exchanger andcondensing at least a portion of the first fluid into water using thefirst heat exchanger. A second heat exchanger may be supplied with atleast one of the fluid output from the fuel cell and the water condensedby the first heat exchanger. Further, the method can comprise cooling afluid flowing through the second heat exchanger, and supplying thecooled fluid to the fuel cell.

Additional objects and advantages of the present disclosure will be setforth in part in the description which follows, and in part will beobvious from the description, or may be learned by practice of thepresent disclosure. The objects and advantages of the present disclosurewill be realized and attained by means of the elements and combinationsparticularly pointed out in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the systems, devices, and methods, asclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thepresent disclosure and together with the description, serve to explainthe principles of the present disclosure.

FIG. 1 provides a schematic representation of a cooling system,according to an exemplary disclosed embodiment that comprises arecirculation loop.

FIG. 2 provides a schematic representation of a cooling system,according to another exemplary disclosed embodiment that comprises tworecirculation loops.

FIG. 3 provides a schematic representation of a cooling system,according to another exemplary disclosed embodiment that comprises aheat exchanger configured to separate and condense water.

FIG. 4 provides a schematic representation of a cooling system,according to another exemplary disclosed embodiment that comprises aheat exchanger with downward fluid flow.

FIG. 5 provides a chart of heat duty provided by the heat exchangers,according to an exemplary disclosed embodiment.

FIG. 6 provides a chart of water balance and heat duty provided by theheat exchangers, according to another exemplary disclosed embodiment.

FIG. 7A provides a schematic representation of a front view of a heatexchanger, according to an exemplary disclosed embodiment.

FIG. 7B provides a schematic representation of a back view of a heatexchanger, according to an exemplary disclosed embodiment.

FIG. 8A provides a schematic representation of a cut-away view of partof a heat exchanger, according to an exemplary disclosed embodiment.

FIG. 8B provides a schematic representation of a back view of part of aheat exchanger, according to an exemplary disclosed embodiment.

FIG. 9A provides a schematic representation of a complete filterassembly, according to an exemplary disclosed embodiment.

FIG. 9B provides a schematic representation of an exploded-view of afilter assembly, according to an exemplary disclosed embodiment.

FIG. 9C provides a schematic representation of a side-view of a filterassembly, according to an exemplary disclosed embodiment.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

FIG. 1 provides a schematic representation of a cooling system 10 of thepresent disclosure for use with a fuel cell 12. In some embodiments,fuel cell 12 can comprise a cathode water injection (CWI) type of fuelcell, whereby cooling water can be supplied to a cathode 16. In otherembodiments, fuel cell 12 can comprise another type of fuel cell.

Fuel cell 12 can comprise an anode 14 fluidly connected to an anodeinlet passage 18 and an anode outlet passage 20. Anode inlet passage 18can be configured to supply hydrogen to anode 14. Outlet passage 20 maybe fluidly connected to inlet passage 18 to at least partiallyrecirculate hydrogen through anode 14.

Cathode 16 can be fluidly connected to a cathode inlet passage 22 and acathode outlet passage 24. Cathode inlet passage 22 can comprise apassage 22 a configured to supply air to cathode 16 and a passage 22 bconfigured to supply water to cathode 16. Outlet passage 24 may befluidly connected to inlet passage 22 to at least partially recirculatewater through cathode 16. One of ordinary skill will recognize that fuelcell 12 can be supplied with recirculated or fresh sources of hydrogen,air, and water using various configurations of one or more passages.

Cooling system 10 can comprise a first heat exchanger 26 and a secondheat exchanger 28. Heat exchangers 26 and 28 can be configured tocondense, separate, trap, or cool water supplied to them in gas, vapor,or liquid form. Heat exchangers 26 and 28 may also be fluidly connectedto one or more passages of cooling system 10. For example, first heatexchanger 26 may be fluidly connected to outlet passage 24 of fuel cell12 and second heat exchanger 28 may be fluidly connected to inletpassage 22 b of fuel cell 12.

Cooling system 10 can also comprise other devices, such as, a waterseparator 30, a storage device 32, a pump 34, or a filter 36. Waterseparator 30 can be configured to at least partially separate water froma flow of fluid entering water separator 30. Storage device 32 can beconfigured to store water, and may comprise a tank, a large-diameterpassage, or an expandable reservoir. Pump 34 can be configured to move afluid through a passage. Filter 36 can be configured to at leastpartially separate particulate matter, ions, or other unwantedcomponents from a fluid. Cooling system 10 can also comprise one or morevalves (not shown) or other fluidic devices.

The embodiments shown and described herein are exemplary, and otherconfigurations are possible based on the present disclosure. Forexample, one or more of the devices described herein may not be requiredor may be arranged in various configurations throughout cooling system10. It is also contemplated that one or more functions of these devicesmay be incorporated into cooling system 10 using these or other devices.

As shown in FIGS. 1-4, outlet passage 20 can comprise a water separator30 a configured to separate a portion of water contained within outletpassage 20. FIGS. 1, 2, and 4 show outlet passage 24 with a waterseparator 30 b, while FIG. 3 shows outlet passage 24 lacking waterseparator 30 b. Water separator 30 a may operate to supply water towater separator 30 b, as shown in FIGS. 1, 2, and 4, or storage device32, as shown in FIG. 3. Water separator 30 b may operate to supply waterto storage device 32 via a first outlet passage 23. Water separator 30 bmay also be configured to supply a fluid to a second outlet passage 25.In some embodiments, the fluid supplied to second outlet passage 25 maycomprise water in a gaseous, vapor, or droplet form.

Second outlet passage 25 may be fluidly connected to first heatexchanger 26 and configured to provide first heat exchanger 26 with afluid. The fluid may be predominantly gas as water may have beengenerally removed from the fluid by water separator 30 b. At least someof the water remaining in the fluid may be condensed or separated byfirst heat exchanger 26. Water retained by first heat exchanger 26 canbe supplied to storage device 32 and recirculated through cooling system10 via a recirculation loop 44. Water flowing through recirculation loop44 may be cooled by second heat exchanger 28 before returning to fuelcell 12. As explained below, first heat exchanger 26 can be operatedgenerally independently of second heat exchanger 28 to improve theoverall operation and efficiency of cooling system 10.

Heat exchanger 26 can comprise one or more components configured tocontrol a temperature of a fluid entering, within, or exiting heatexchanger 26. For example, heat exchanger 26 can comprise one or morefans 38 configured to control the temperature of a fluid passing into anexhaust passage 40. Specifically, heat exchanger 26 can comprise twocooling fans (see FIG. 7A).

By controlling fluid temperature, a rate of water condensation can beselectively controlled. Further, the amount of water within coolingsystem 10 can be adjusted by supplying the water retained within heatexchanger 26 to cooling system 10. Over time this water balance can bemaintained within a desired range so that the total amount of waterwithin cooling system 10 is generally constant. Such “water neutrality”means that cooling system 10 can operate with little or no water beingsupplied by external sources. This can include producing water via fuelcell 12 at a rate that is about equal to the rate of water loss viaexhaust passage 40. A short-term mismatch in the rates of waterproduction and loss can be buffered by supplying excess water to storagedevice 32 or removing water from storage device 32.

Heat exchanger 26 can comprise one or more outlet passages 42 configuredto supply water to cooling system 10. As shown in FIG. 1, storage device32 can by supplied with water from water separator 30 b via outletpassage 23 and heat exchanger 26 by outlet passage 42. Water storedwithin storage device 32 may be supplied to second heat exchanger 28 bypump 34. Second heat exchanger 28 may at least partially cool the waterbefore it passes through filter 36 and into inlet passage 22 b. Thus,heat exchanger 28 may control the water temperature before the water isdirected back into cathode 16.

As shown in FIG. 2, according to another exemplary embodiment, coolingsystem 10 can comprise a second recirculation loop 46 for cooling waterin recirculation loop 44. Specifically, second recirculation loop 46 canbe fluidly connected to recirculation loop 44 such that at least part ofthe water supplied to recirculation loop 44 can be supplied torecirculation loop 46. While in recirculation loop 46, water can becooled by second heat exchanger 28 as described above. It is alsounderstood that recirculation loop 46 may or may not comprise storagedevice 32, pump 34, or other device of cooling system 10.

FIG. 3 provides a schematic representation of cooling system 10,according to another exemplary embodiment, wherein outlet passage 24from fuel cell 12 is in direct fluid communication with first heatexchanger 26. In this configuration, fluid output from cathode 16 issupplied directly to first heat exchanger 26 without passing through awater separator. First heat exchanger 26 can thus function as a waterseparator to separate water from fluid output by cathode 16. Wateroutput by water separator 30 a can be directly supplied to storagedevice 32. Such a configuration could also be provided with otherembodiments of cooling system 10 described herein.

FIG. 4 provides a schematic representation of cooling system 10,according to another exemplary embodiment, wherein first heat exchanger26 comprises a downward flow path. As explained below, first heatexchanger 26 can be configured to operate with an upward flow path or adownward flow path.

In an upflow design, for example as shown in FIGS. 1-3, fluid suppliedfrom outlet passage 24 or water separator 30 b can enter a lowermanifold 48 located in a lower region of first heat exchanger 26. Thefluid may then flow through first heat exchanger 26 in a general upwarddirection to an upper manifold 50 located in an upper region of firstheat exchanger 26. This upward flow path can allow water condensingwithin first heat exchanger 26 to flow downwards due to gravity, againstthe upflow of the fluid. The condensed water can then drain out of lowermanifold 48 and into storage device 32 via outlet passage 42.

In a downflow design, for example as shown in FIG. 4, fluid from fuelcell 12 can enter first heat exchanger 26 via upper manifold 50. Thefluid may then flow in a general downward direction to lower manifold 48and exit first heat exchanger 26 via exhaust passage 40. Water condensedin first heat exchanger 26 can also flow generally downwards and maydrain out of lower manifold 48 via outlet passage 42.

As previously discussed, cooling system 10 may offer greater designflexibility than traditional cooling systems. Cooling system 10 maycomprise less components, simplified plumbing, or occupy less space thantraditional systems. In operation, cooling system 10 may also provideone or more other advantages over traditional systems, such asindependent control of water temperature and water balance. Further,cooling system 10 may permit adjusting the split of total heat loadbetween heat exchangers 26 and 28 to improve cooling performance oroperating range.

For situations when the water balance of cooling system 10 is generallyconstant, the total heat rejected by cooling system 10 can be relativelyconstant over a range of operating conditions of fuel cell 12. In thesesituations, cooling system 10 can be configured to split the total heatrejection required to cool fuel cell 12 between heat exchangers 26 and28. This split can be controlled by adjusting an operating parameter offuel cell 12 or cooling system 10, such as, for example, airstoichiometry, water inlet temperature of cathode 16, or flow rate ofcooling water 22 b.

For example, FIG. 5 shows operating parameter options for a fuel cellsystem requiring approximately 15 kW of total heat rejection to achievea positive water balance of about 0.4 g/s. By changing the operatingparameters as indicated in Table 1 (air stoichiometry about 1.5 to about2.5, water temperature about 55 to about 65° C., water flow rate about15 to about 25 ml/hr/Amp/cell), the heat duty split between first heatexchanger 26 (HX1) and second heat exchanger 28 (HX2) can range fromabout 25%/about 75% to about 78%/about 22%.

TABLE 1 Example Fuel Cell Operating Parameter Options Water Total FlowWater Heat HX1 HX2 HX1 HX2 Air Rate Temp Duty Duty Duty Duty Duty LabelStoichiometry (g/s) (° C.) (kw) (kW) (kW) (%) (%) A ~1.5 ~25 ~55 ~14.8~3.7 ~11.1 ~25 ~75 B ~2.5 ~15 ~65 ~15.8 ~12.4 ~3.4 ~78 ~22

Cooling system 10 can operate using a more restrictive or a lessrestrictive range of operating conditions by limiting one or moreoperating parameters. For example, as shown in FIG. 5, limiting the airstoichiometry to about 1.75 to about 2.25 (points C&D), instead of about1.50 to about 2.50 (points A & B), while maintaining the same range ofwater flow and temperature may reduce a maximum required load on firstheat exchanger 26 from about 12.4 to about 11.7 kW and on second heatexchanger 28 from about 11.1 to about 10.3 kW. Further limiting waterflow and temperature may further reduce operational requirements for oneor both heat exchangers 26 and 28.

Cooling system 10 can also be operated to control a water balance withina desired range. For example, by increasing the total heat duty rejectedthrough heat exchangers 26 and 28, more water can be condensed by firstheat exchanger 26. A positive water balance can be created whereby morewater is provided by first heat exchanger 26 such that the total amountof water contained in cooling system 10 increases. FIG. 6 shows how theheat duty rejected through heat exchangers 26 and 28 can be adjusted toprovide a positive or neutral water balance.

In some instances, lowering the total heat duty can create a neutral ornegative water balance. For example, first heat exchanger 26 can providea generally neutral water balance by condensing water or controlling atemperature of fluids passing through exhaust passage 40 such that therate of water exiting cooling system 10 is about equal to the rate ofwater produced in the fuel reaction between hydrogen and oxygen. If thetotal amount of water in cooling system 10 exceeds a desired level,first heat exchanger 26 can operate to remove more water from coolingsystem 10 via exhaust passage 40 than is produced in the fuel cellreaction. This feedback control can be used to maintain a desiredquantity of water in cooling system 10. Specifically, a desired level ofwater in storage device 32 can be maintained by controlling the amountof water leaving cooling system 10 via exhaust passage 40.

In some embodiments, the heat duty of first heat exchanger 26 can remaingenerally constant for a fixed set of operating parameters. With agenerally constant heat duty of second heat exchanger 28, the waterbalance can be adjusted by changing the heat duty of first heatexchanger 26. For example, by changing a fan speed of first heatexchanger 26 and thus changing the temperature and water vapor contentof fluid flowing through exhaust passage 40. Similarly, for a fixed heatduty of first heat exchanger 26, the water balance can be adjusted bychanging the cathode air stoichiometry.

In situations where the heat duty balance requires further manipulation,the operating parameters can be shifted to improve the water balance.For example, if cooling system 10 operates in a hot environment and isunable to condense enough water, an operating parameter could beadjusted to shift more of the heat duty to second heat exchanger 28.This shift in heat duty may lessen the cooling required by first heatexchanger 26 and improve the ability of first heat exchanger 26 tomaintain the water balance. If cooling system 10 operates in a coldenvironment and condenses too much water, the rate of condensation canbe reduced by adjusting an operating parameter to shift heat duty fromsecond heat exchanger 28 to first heat exchanger 26. This shift may keepthe exhaust gas hot enough to carry excess water out of first heatexchanger 26 at exhaust passage 40.

FIGS. 7A and 7B provide schematic diagrams of first heat exchanger 26,according to an exemplary embodiment. As described above, first heatexchanger 26 can be configured to convert at least a portion of watervapor passing through first heat exchanger 26 into liquid form. Forexample, first heat exchanger 26 may be configured to flow an input gasstream upward against gravity. At the same time liquid water, that waseither entrained with the input gas or condensed from the input gas, canflow downward due to gravity. As such, first heat exchanger 26 canfunction as condensing unit or a water separator.

As shown in FIGS. 7A and 7B, first heat exchanger 26 can comprise lowermanifold 48 and upper manifold 50. Lower manifold 48 can comprise aninlet port 52 for receiving a flow of fluid output from fuel cell 12(not shown). Lower manifold 48 may also comprise one or more drain ports54 configured to provide an outlet for water retained by first heatexchanger 26. In some embodiments, drain ports 54 can be located towardopposite ends of lower manifold 48 to provide efficient water drainagewhen “sloshing” may push water toward either side of lower manifold 48.Such sloshing may occur due to motion of a vehicle using cooling system10.

It is also contemplated that first heat exchanger 26 may operate withoutdrain port 54. For example, an inlet passage (not shown) supplying fluidfrom water separator 30 b may be angled upward toward drain port 54. Theupward-angled inlet passage may also be sized to keep gas velocitieslow, as described below. Such an inlet passage may permit at least somewater trapped by first heat exchanger 26 to drain back into waterseparator 30 b.

As shown in FIGS. 8A and 8B, heat exchanger 26 can comprise one or morechannels 56 configured to direct fluid through heat exchanger 26. Insome embodiments, channels 56 can be generally vertical and may extendfrom lower manifold 48 to upper manifold 50. The configuration ofchannels 56 can permit fluid to flow generally upward from lowermanifold 48 to upper manifold 50. Channels 56 can also be configured topermit fluid to flow generally downward, as described above for FIG. 4.

Channels 56 may be configured to collect water or allow water to drainout of first heat exchanger 26. For example, one or more channels 56 maybe sized to allow liquid water to run downward due to gravity whilefluid flows upward through channel 56. To achieve this result, thevelocity of the fluid in channel 56 may be kept sufficiently low toreduce drag forces so that they are insufficient to push water upwardwith the fluid flow. In particular, channels 56 may be sized to provideenough total cross-sectional area (number of channels x cross sectionalarea of each channel) to limit the fluid velocity to a sufficiently lowlevel to allow water drainage. Channels 56 may also have dimensions thatare large enough to generally limit water surface tension that may holdwater in place even with low fluid velocity. For example, channel 56 mayhave a width of about 6 mm or more. Water trapped within channels 56 maycollect in lower manifold 48 and flow out of drain port 54, as shown inFIGS. 7A and 7B.

In some embodiments, heat exchanger 26 can comprise one or moregenerally parallel channels 56 directed generally vertically. Theparallel channels 56 can each be fluidly connected to upper manifold 50.Upper manifold 50 can comprise a lumen 58 fluidly connected to one ormore channels 56 and configured to direct a flow of fluid to an exhaustport 60, as shown in FIG. 8A.

Under some operating conditions, liquid water may be present in a flowof fluid within upper manifold 50. One or more features of heatexchanger 26 can be configured to generally limit liquid water flowingout of exhaust port 60. For example, exhaust port 60 may be sufficientlylarge in cross-sectional area to generally maintain a low gas velocity.In another example, exhaust port 60 may comprise a filter assembly 62that may filter the flow of water through port 60.

Filter assembly 62 may be configured to allow exhaust fluid to exitcooling system 10 via first heat exchanger 26. Filter assembly 62 mayalso be configured to limit the passage of water out of first heatexchanger 26 or limit entry of external dirt or debris into first heatexchanger 26. In addition, filter assembly 62 may be configured topermit water that condenses or coalesces on filter assembly 62 to drainback into first heat exchanger 26.

FIGS. 9A-C provide schematic diagrams of filter assembly 62, accordingto an exemplary embodiment. Filter assembly 62 can comprise one or morefilter elements 64, filter frames 66, or gaskets 68 positioned invarious configurations. In general, one or more filter elements 64 canpermit fluid to exit cooling system 10 while at least partially limitingthe passage of liquid water through filter assembly 62. Such filteringmay, in some circumstances, prevent the expulsion of liquid water withthe exhaust gas exiting first heat exchanger 26.

As shown in FIG. 9B, filter assembly 62 can comprise, three filterelements 64, three filter frames 66, and one gasket 68 located adjacentto each other. Filter element 64 can comprise one or more layers ofporous media, such as, for example, a metallic foam, a mesh, or a feltmedia. One or more filter elements 64 can be held between one or morefilter frames 66 or gaskets 68. In some embodiments, a first and thirdfilter element can comprise an about 1.2 mm metallic foam and a secondfilter element can comprise Bekipor 60BL3 metallic filter media of otherBekipor filter media. Generally, filter element 64 should 1) enablegases including water vapor to pass through, 2) coalesce or block liquidwater, 3) provide liquid water drainage, or 4) minimize infiltration ofexternal dust or debris into heat exchanger 26. Filter element 64 caninclude a foam, screen, mesh, felt, wool, paper, or other porousstructure. These can be formed in part from a material including metal,Teflon, glass fiber, cloth, or ceramic. In addition, filter frame 66separating a first and second filter element 64 can have a width ofabout 5 mm.

In some embodiments, first heat exchanger 26 or filter assembly 62 canbe configured to drain at least some water trapped by filter assembly 62back into first heat exchanger 26. For example, the porous nature offilter element 64 may provide a path for liquid water to drain intolumen 58 due to gravity. First heat exchanger 26 or filter assembly 62can be variously configured to permit trapped water to drip back intoone or more channels 56 (not shown). To assist this water flow, filterframe 66 located between two filter elements 64 may not cover at least apart of a bottom edge 70 of filter element 64, as shown in FIG. 9C.Further, bottom edges 70 of filter elements 64 may be located above oneor more channels 56 so that water from filter assembly 62 can drip inchannels 56. As described above, channels 56 can be sized to enablewater to flow downward to lower manifold 48.

Other embodiments of the present disclosure will be apparent to thoseskilled in the art from consideration of the specification and practiceof the concepts disclosed herein. For example, first heat exchanger 26may be used with various fuel cells, such as, for example, a coolingcell style fuel cell system. Moreover, one or more functions orcomponents of heat exchangers 26 and 28 may be combined into a singleunit. It is intended that the specification and examples be consideredas exemplary only, with a true scope and spirit of the presentdisclosure being indicated by the following claims.

What is claimed is:
 1. A method of cooling a fuel cell, comprising:supplying hydrogen to an anode of the fuel cell and supplying air andwater to a cathode of the fuel cell; outputting a fluid from the fuelcell, wherein at least a portion of the fluid comprises a first fluid;supplying the first fluid to a first heat exchanger and condensing atleast a portion of the first fluid into water using the first heatexchanger; supplying to a second heat exchanger the water condensed bythe first heat exchanger; cooling the water condensed by the first heatexchanger while flowing through the second heat exchanger; and supplyingthe cooled water to the fuel cell; wherein the cathode is connected to acathode outlet passage having a first water separator configured tosupply the first fluid to the heat exchanger.
 2. The method of claim 1,further comprising separating water from hydrogen recirculated throughthe anode, wherein the water is separated by a second water separatorthat supplies the water to the first water separator.
 3. The method ofclaim 2, wherein water separated by the first water separator and thefirst water separator is supplied to a storage device.
 4. The method ofclaim 1, further comprising circulating the water condensed by the firstheat exchanger through a storage device.
 5. The method of claim 4,wherein a rate of the water condensed by the first heat exchanger andoutput to the storage device is controlled by controlling a temperatureof the first fluid passing through the first heat exchanger.
 6. Themethod of claim 1, comprising independently controlling a watertemperature of the cooled water supplied to the fuel cell and a waterbalance of the fuel cell.
 7. The method of claim 1, further comprisingmodifying an operating parameter to balance a heat duty of the firstheat exchanger and the second heat exchanger, wherein the operatingparameter comprises at least one of a water balance, a cathodestoichiometry, a fluid flow rate, and a fluid temperature.
 8. The methodof claim 7, wherein modifying the operating parameter modifies a rate ofwater vapor exiting the first heat exchanger to at least partiallycontrol a level of stored water.
 9. The method of claim 1, wherein thefirst heat exchanger is part of a first recirculation loop forcirculating the cooled water to the cathode of the fuel cell and thesecond heat exchanger is part of a second recirculation loop fluidlyconnected to the first recirculation loop.
 10. The method of claim 1,further comprising creating a positive water balance by increasing atotal heat duty rejected through the first heat exchanger with agenerally constant heat duty of a second heat exchanger.
 11. The methodof claim 9, further comprising creating a negative water balance bylowering a total heat duty rejected through the first heat exchanger.12. The method of claim 1, further comprising creating a neutral waterbalance by adjusting the total heat duty rejected through the first heatexchanger such that a rate of water vapor exiting the first heatexchanger is about equal to a rate of water produced by the fuelreaction in the fuel cell.